Throttle operating devices have long been employed in automotive and other vehicular internal combustion engines. These operating devices typically include a throttle lever attached to a throttle shaft and operatively connected to an associated throttle control linkage. The throttle control linkage is operatively connected to a foot-operated throttle pedal or "accelerator" or to another type of operator-actuated throttle control element within the vehicle's passenger compartment. This permits the operator to control the action of a fuel supply system, such as a fuel injection system or throttle valve, through the throttle control linkage and associated throttle lever simply by pressing down or releasing the throttle pedal or by moving the throttle control element.
Throttle levers are normally arranged to move between two positions: an idle position wherein sufficient fuel is supplied to the engine so that it will run at a predetermined idling speed, and a full throttle position wherein a maximum amount of fuel is supplied to the engine. The idle and full throttle positions are normally defined by adjustable stops. When the accelerator is fully depressed or the throttle control element is fully advanced, the fuel supply control is in a full throttle position, and the engine is capable of running at a high speed. A return spring is typically used to bias the throttle lever to the setting required to maintain a preset engine idle speed when pressure on the throttle pedal is released or when the throttle control is fully retracted.
Various structures have been proposed to insure control over engine throttling and to avoid the creation of an "uncontrolled" engine wherein the operator loses control over the position of the throttle shaft. One circumstance which can overstress the throttle lever and potentially lead to loss of throttle shaft control occurs when the throttle shaft encounters a stop while continued advancing force is applied to the throttle lever through the throttle control linkage. Typically a "breakover" mechanism is provided in situations of this sort to protect the throttle shaft against such excessive force. The throttle lever breakover capability will be activated when, for example, a vehicle driver continues to exert force on an accelerator pedal or throttle control element after the throttle shaft has reached its full throttle position.
Two part throttle levers, one part of which is pivotally mounted with respect to the other to form a lever link, are normally used to provide the breakover function. The lever link is able to move or "break over" independently of the throttle lever when conditions require breakover capability. A torsion spring is typically provided on the throttle lever to urge the lever link toward its normal position and to return the lever link to its normal position upon release of the breakover causing force.
High pressure fuel pump throttle shafts and components are particularly susceptible to damage if a throttle lever is not capable of independent movements in response to a breakover-causing force.
The prior art has proposed various types of throttle levers with breakover functions that limit breakover travel or return the engine throttle system to the idle position. For example, in U.S. Pat. No. 3,760,786 to Marsh, a throttle return system is disclosed, including a two part lever and a coiled safety spring, which returns a throttle valve to the desired idle setting in the event of a failure of either the throttle return spring or the associated throttle control linkage. The central pivot connection of the two levers in this system allows a long travel distance between the idle and full throttle positions. Consequently, this system does not function as efficiently as might be desired, and the distance the throttle linkage elements are required to travel, particularly in the event of a malfunction, could damage the fuel pump internal components.
One known throttle lever design includes a one way breakover mechanism to permit over travel of the throttle linkage when the throttle shaft reaches its full throttle position. This known design includes a torsion spring for biasing a link lever toward its normal operating position and for transmitting the spring biasing force to the link lever. A stop pin, mounted on the link lever, is arranged to be engaged by one end of the torsion spring and to form a stop to define the normal operating position of the link lever relative to the throttle lever. This throttle lever design has some limitations, however. It can be installed by the end user in a way that may overstress the throttle lever torsion spring and cause it to break. As in the design disclosed in the Marsh patent, the throttle lever and link lever are pivotally connected by a centrally located pivotal connector, which produces a long travel stroke.
U.S. Pat. No. 4,928,647 to Villanyi et al. discloses a reliable dual-acting double breakover throttle lever which overcomes some of the disadvantages of the foregoing throttle lever design and provides breakover capability in both idle and full throttle conditions. However, the central pivotal connection of this assembly also produces a long travel stroke and requires longer throttle control linkages than may be desirable in some engine applications.
The throttle assemblies of the prior art typically provide a relatively large amount of "play" in the travel of the throttle lever and associated assembly components. To achieve this, the accelerator pedal or throttle control must be several inches from the floor of the vehicle, and connecting linkage structures are somewhat long and cumbersome. Reduction of the travel distance of the throttle lever and associated structures would provide a more compact and more efficient fuel throttling assembly.
The prior art, therefore, has failed to provide an efficient short stroke breakover throttle lever assembly for use with an internal combustion engine high pressure fuel pump that is capable of allowing overtravel of the throttle rod or linkage without damage to the fuel pump throttle lever or internal pump components.